This invention relates to the field of automated instruments designed for handling culture plates, also known in the art as agar plates.
In the field of microbiology, automated instruments are known which streak a specimen onto a growth medium such as agar which is placed within a culture plate. The culture plate is typically in the form of a Petri dish. The streaked plate is then incubated. The presence of microbial colonies in the plate after incubation indicates that the microbe was present in the original specimen. Instruments for handling culture plates and streaking specimens onto a growth medium are described in U.S. Pat. No. 4,287,301; U.S. Pat. No. 6,617,146 and U.S. patent application publication 2007/0202564. The content of these patent documents is incorporated by reference herein.
In a lab where an instrument such as described in the above-referenced patent documents is installed, a lab technician typically is working with many plates at a time, retrieving plates from refrigerated storage, sorting them, etc., and otherwise manually handling them on the lab bench. Manufacturers of culture plates typically provide features in the bottoms of the plates and in the lids of the plates such that the plates can be nested, and thus stacked one on top of the other, without the plates sliding all around and falling over. For example, the outer edge of the bottom of the plate is sized and shaped so as to just fit within the cover or lid for the plate. That way, a group of plates can be nested and stacked on top of each other, either right-side up (cover up) or upside down (cover down).